1. Field of the Invention
The present invention relates to a liquid crystal display device used for a portable personal computer, etc. particularly to a liquid crystal display device having a magnifying or enlarging display function.
2. Description of Prior Arts
A liquid crystal display device is employed as a display device of various electronic devices such as a laptop-type or a note-book-type portable personal computer, a word processor, a portable TV, a video camera or the like since it is thin, light and consumes little power.
Such a liquid crystal display device (LCD device) generally comprises a liquid crystal display (LCD) composed of a liquid crystal display panel (LCD panel) provided with a plurality of liquid crystal pixels arranged as a matrix and display electrodes corresponding to the liquid crystal pixels and a driving circuit for driving the liquid crystal pixels under time-sharing control, namely, for time-sharing matrix driving the liquid crystal pixels by successively applying control signals corresponding to the image data to the display electrodes forming each line of the image data; and, a display controller for outputting the image data and synchronous signals to the driving circuit.
Moreover, such an LCD device has enlarging function, which is not only effective in fine visibility but also in improvement of contrast or reduction of power consumption.
As a result, enlarging display methods have been proposed using the LCD device.
For example, Japanese Patent Laid-Open Publication No. 55-79492 discloses an enlarging display method comprising applying the same driving signal to a plurality of display electrodes in a bunch or unit so as to change the size of the displayed unit of pixels to thereby enlarge a display area. Furthermore, Japanese Patent Laid-Open Publication No. 57-68979 discloses a method of enlarging the display area by N times by increasing the frequency of a scanning clock by N times for time-sharing matrix driving of liquid crystal pixels of an LCD device, and a method of changing display areas by delaying reference signals.
Such conventional enlarging display methods, however, cannot enlargedly display an image from any desired display area of a full-screen area of a display, but normally only an image from, e.g. an upper screen area, can be enlargedly displayed on a full-screen area of a display.
Still furthermore, there is an LCD of a vertically-divided driving system shown in FIG. 14, wherein image data is inputted independently to upper and lower half portions of the LCD.
According to this example, an LCD 1 is provided with an LCD panel 2, which can display image data corresponding to 400 rows of pixels (hereinafter referred to as 400 lines of image data). The LCD 1 independently comprises a 4-bit parallel-input upper data bus 12 for transferring upper side image data corresponding to 200 rows of pixels extending from the 1st through 200th rows (hereinafter referred to as the 1st through 200th image data lines) to be displayed on an upper half portion 2a of the LCD panel 2, and a 4-bit parallel-input lower data bus 13 for transferring a lower side image data corresponding to 200 rows of pixels extending from 201st through 400th rows (hereinafter referred to as 201st through 400th image data lines) to be displayed on a lower half portion 2b of the LCD panel 2.
Synchronous signals for scanning and time-sharing matrix driving each liquid crystal pixel are inputted into the upper half portion 2a and the lower half portion 2b by way of the same bus, i.e., a synchronous bus 14 wherein both upper and lower half portions 2a and 2b are scanned at the same time 200 times per cycle, thereby displaying 400 lines of image data extending from the 1st through 400th lines image data.
Such an LCD had a problem in that when an image from any desired display area of a full-screen area is to be enlarged, the image data is not equally divided into upper and lower side image data so that the enlarged image becomes discontinuous or uneven.